This invention relates to an improved method and apparatus for testing and indicating the condition of shock absorbers in situ on automotive vehicles, particularly automobiles. More particularly, the invention relates to apparatus of the described type which is portable and which carries its own source of energy for operating it.
In the past, various different methods and apparatus have been proposed for testing shock absorbers in situ on automotive vehicles, however, most, if not all, of them have not been commercially acceptable for one reason or another. One such apparatus is disclosed in U.S. Pat. No. 3,164,003, issued to C. W. MacMillan on Jan. 5, 1965. The disclosed shock absorber tester comprises a jack-type apparatus for lifting the car body and then dropping it to set it into oscillation, and sensing means for measuring the number and amplitude of the oscillations to obtain an indication of shock absorber condition. While the MacMillan device provides an accurate initial displacement, it comprises a very heavy and bulky apparatus. It is certainly not portable in the sense that it can be transported and, particularly, it cannot be hand-carried from place to place. Furthermore, the MacMillan device does not provide a record of the number of oscillations. The operator must not take his eyes off the indicator pointer and must remember the number and amplitude of its swings.
A similar apparatus is disclosed in U.S. Pat. No. 3,456,489, issued to S. J. Levenson, on July 22, 1969. Levenson uses an accelerometer-type sensor which is placed upon the hood of an automobile and is connected to an indicator panel which serves to analyze the number and magnitude of the oscillations. Levenson's apparatus, like MacMillan's, certainly is not portable. Also, he does not disclose the details of the sensor, analyzer or indicator panel, hence it is not clear exactly what quantity is being measured.
In U.S. Pat. No. 3,313,142, issued to B. C. Lackman, on Apr. 11, 1967, it is illustrated in FIGS. 10 through 13 a testing apparatus adapted to be placed upon an automotive fender or hood. The car is then driven over a ramp of predetermined size in order to place the sprung portion of the automobile body into vertical oscillations from a predetermined displacement, the oscillations being measured by a sensor to produce an output indication at the total time that the car is in motion in a given vertical direction. The accuracy of this particular apparatus is questionable, since the automobile must be driven or otherwise moved in a forward direction over a ramp during the testing procedure in order to perform the test.
Other similar apparatus for testing shock absorbers in situ on automotive vehicles are disclosed in U.S. Pat. Nos. 3,157,044; 3,383,909; 3,857,276; 3,902,352; 3,906,779 and 3,939,692. The apparatus disclosed in each of these patents generally suffer from the same disadvantages found with the apparatus disclosed in the above-mentioned patents to MacMillan, Levenson and Lackman.